Measurement
In physics, we basically do measurement on all things that can measured. We see a phenomenon or an object, we observe it, take a measurement, and make a mathematical model for describe and predict the behavior of those things.
Since ancient times, Human love to compare things. Imagine if we want to take a free pizza from a party, we would try to see which one is bigger or smaller piece, and of course we will take a bigger piece, right? but how do we know it is bigger that the other piece? simple, just compare it with other piece and you can tell by just looking at it. hey it is a bigger pizza.
Then, there is a question, if something is big, how big is it? If something is long, how long is it compared to another one? Which one is actually bigger? We cannot just say “big” or “small” without knowing how much, right? So we need a way to compare a quantity with another quantity of the same kind. From there, math number is introduced to define and express that quantity clearly.
lets take an example, there is a book and there are identical pens. how we can define how long that book is? we can put pens in row along book and we can tell
“Hey, the book is two pens long”. The length of the book, which is what we measure, is called a quantity. The pen is the object we use as a comparison, which we call a unit, and 2 is the measurement value. With this, we know the length of the book equals the length of 2 pens.
That is measurement. Measurement is the process of comparing a object quantity with another object as a unit. We only can do measurement with comparing quantity with same quantity. length book with length pen, weight with weight, and much more.
The Systeme International (SI) of Units
Imagine we take a measurement like in the example before. Lets say our friend measures the same book using his own pen as a unit of comparison. There is a problem here are the length of his pen might be different from ours, right? If that happens, the measurement value can change. The book might be measured as 3 pens long simply because his pen is smaller. This can lead to confusion.
Now, let’s say another friend measures the same book, but instead of using a pen, he uses a marker, which is a totally different unit. He might find that the length of the book is one and a half markers, while we got a result of 2 pens. This means we can try to convert our unit (length of pen) into his unit (length of marker), which sounds great. However, there is a problem, the conversion process can lead to inaccuracy.
This problem actually happened in the real world. Since ancient times, humans traded using different units from different cultures and regions, which made conversion and price determination difficult. The inconsistency of units often led to fraud and unfairness in trade. This also happened in Ancien Régime, where until 1795, France used many different systems of measurement without a unified standard. There was even widespread abuse of measurement standards for taxation and trade.
The solution to this problem was the creation of a standardized and universal system called the metric system. Thanks to the French Revolution, this system was introduced and later became the foundation of the system are used today. Not go too deep into the history here.
The International System of Units (SI), which consists of 7 base units and its quantity that are widely used by many countries around the world
| Quantity | Unit Name | Symbol | Dimension |
|---|---|---|---|
| Length | meter | m | [L] |
| Mass | kilogram | kg | [M] |
| Time | second | s | [T] |
| Electric Current | ampere | A | [I] |
| Temperature | kelvin | K | [Θ] |
| Amount of Substance | mole | mol | [N] |
| Luminous Intensity | candela | cd | [J] |
Each unit has its own definition and history. For example, for mass, it is used a physical prototype made of a platinum–iridium cylinder called the kilogram. One kilogram was defined as the mass of that cylinder. This prototype was copied and distributed to many countries as the international standard of mass.
Of course, each definition has been updated over time as technology advances. The more of history of these developments on the official website of the International Bureau of Weights and Measures, the international organization responsible for maintaining these standards